The pacmanpackage manager is one of the major distinguishing features of Arch Linux. It combines a simple binary package format with an easy-to-use build system. The goal of pacman is to make it possible to easily manage packages, whether they are from the official Arch repositories or the user's own builds.

Pacman keeps the system up to date by synchronizing package lists with the master server. This server/client model also allows you to download/install packages with a simple command, complete with all required dependencies.

Pacman is written in the C programming language and uses the .pkg.tar.xz package format.

Tip: The official pacman package also contains other useful tools, such as makepkg, pactree, vercmp and more. You can get the full list from pacman -Ql pacman | grep bin

Configuration

Pacman's settings are located in /etc/pacman.conf. This is the place where the user configures the program to work in the desired manner. In-depth information about the configuration file can be found in man pacman.conf.

General options

General options are in the [options] section. Read the man page or look in the default pacman.conf for information on what can be done here.

Skip package from being upgraded

To skip upgrading a specific package, specify it as such:

IgnorePkg=linux

For multiple packages use a space-separated list, or use additional IgnorePkg lines.

Skip package group from being upgraded

As with packages, skipping a whole package group is also possible:

IgnoreGroup=gnome

Skip files from being installed to system

To always skip installation of specific directories list them under NoExtract. For example, to avoid installation of systemd units use this:

NoExtract=usr/lib/systemd/system/*

Repositories

This section defines which repositories to use, as referred to in /etc/pacman.conf. They can be stated here directly or included from another file.

All official repositories use the same /etc/pacman.d/mirrorlist file which uses the $repo variable, making it necessary to maintain only one list.

Warning: Care should be taken when using the [testing] repository. It is in active development and updating may cause some packages to stop working. People who use the [testing] repository are encouraged to subscribe to the arch-dev-public mailing list for current information.

Package security

Pacman 4 supports signed packages, which adds an extra layer of security to the packages. To enable signature verification, take a look here.

Usage

What follows is just a small sample of the operations that pacman can perform. To read more examples, refer to man pacman.

Installing packages

Installing specific packages

To install a single package or list of packages (including dependencies), issue the following command:

# pacman -S package_name1package_name2 ...

Sometimes there are multiple versions of a package in different repositories, e.g. [extra] and [testing]. To install the former version, the repository needs to be defined in front:

# pacman -S extra/package_name

Installing package groups

Some packages belong to a group of packages that can all be installed simultaneously. For example, issuing the command:

# pacman -S gnome

will install all the packages that belong to the gnome group. To see what packages belong to the gnome group, run:

Removing packages

To remove a single package, leaving all of its dependencies installed:

# pacman -R package_name

To remove a package and its dependencies which are not required by any other installed package:

# pacman -Rs package_name

To remove a package, its dependencies and all the packages that depend on the target package:

Warning: This operation is recursive, and must be used with care since it can remove many potentially needed packages.

# pacman -Rsc package_name

To remove a package, which is required by another package, without removing the dependent package:

# pacman -Rdd package_name

Pacman saves important configuration files when removing certain applications and names them with the extension: .pacsave. To prevent the creation of these backup files use the -n option:

# pacman -Rn package_name

Note: Pacman will not remove configurations that the application itself creates (for example "dotfiles" in the home folder).

Upgrading packages

Pacman can update all packages on the system with just one command. This could take quite a while depending on how up-to-date the system is. This command can synchronize the repository databases and update the system's packages (excluding 'local' packages that are not in the configured repositories):

# pacman -Syu

Warning: Instead of immediately updating as soon as updates are available, users must recognize that due to the nature of Arch's rolling release approach, an update may have unforeseen consequences. This means that it is not wise to update if, for example, one is about to deliver an important presentation. Rather, update during free time and be prepared to deal with any problems that may arise.

Pacman is a powerful package management tool, but it does not attempt to handle all corner cases. Read The Arch Way if this causes confusion. Users must be vigilant and take responsibility for maintaining their own system. When performing a system update, it is essential that users read all information output by pacman and use common sense. If a user-modified configuration file needs to be upgraded for a new version of a package, a .pacnew file will be created to avoid overwriting settings modified by the user. Pacman will prompt the user to merge them. These files require manual intervention from the user and it is good practice to handle them right after every package upgrade or removal. See Pacnew and Pacsave Files for more info.

Tip: Remember that pacman's output is logged in /var/log/pacman.log.

Before upgrading, it is advisable to visit the Arch Linux home page to check the latest news (or subscribe to the RSS feed): when updates require out-of-the-ordinary user intervention (more than what can be handled simply by following the instructions given by pacman), an appropriate news post will be made.

If one encounters problems that cannot be solved by these instructions, make sure to search the forum. It is likely that others have encountered the same problem and have posted instructions for solving it.

Querying package databases

Pacman queries the local package database with the -Q flag; see:

$ pacman -Q --help

and queries the sync databases with the -S flag; see:

$ pacman -S --help

Pacman can search for packages in the database, searching both in packages' names and descriptions:

$ pacman -Ss string1string2 ...

To search for already installed packages:

$ pacman -Qs string1string2 ...

To display extensive information about a given package:

$ pacman -Si package_name

For locally installed packages:

$ pacman -Qi package_name

Passing two -i flags will also display the list of backup files and their modification states:

One can also query the database to know which package a file in the file system belongs to:

$ pacman -Qo /path/to/file_name

To list all packages no longer required as dependencies (orphans):

$ pacman -Qdt

To list a dependency tree of a package:

$ pactree package_name

To list all the packages depending on a package, use whoneeds from pkgtools:

$ whoneeds package_name

Additional commands

Upgrade the system and install a list of packages (one-liner):

# pacman -Syu package_name1package_name2 ...

Download a package without installing it:

# pacman -Sw package_name

Install a 'local' package that is not from a remote repository (e.g. the package is from the AUR):

# pacman -U /path/to/package/package_name-version.pkg.tar.xz

Install a 'remote' package (not from a repository stated in pacman's configuration files):

# pacman -U http://www.example.com/repo/example.pkg.tar.xz

Clean the package cache of packages that are not currently installed (/var/cache/pacman/pkg):

Warning: Only do this if you are sure that the installed packages are stable and that a downgrade will not be necessary, since it will remove all of the old versions from the cache folder, leaving behind only the versions of the packages that are currently installed. This comes in handy in case a future upgrade causes breakage, because you will have the packages that are working right on your system, ready to be installed.

# pacman -Sc

Clean the entire package cache:

Warning: This clears out the entire package cache. Doing this is considered a bad practice, because if you ever need to downgrade something, you will not be able to do so right from the cache folder. You will probably have to use the Arch Rollback Machine.

# pacman -Scc

Tip: As an alternative to both the -Sc and -Scc switches, consider using paccache from pacman-contrib. This offers more control over what and how many packages are deleted. Run paccache -h for instructions.

Partial upgrades are unsupported

Arch Linux is a rolling release, and new library versions will be pushed to the repositories. The developers and Trusted Users will rebuild all the packages in the repositories that need to be rebuilt against the libraries. If the system has locally installed packages (such as AUR packages), users will need to rebuild them when their dependencies receive a soname bump.

This means that partial upgrades are not supported. Do not use pacman -Sy package or any equivalent such as pacman -Sy and then pacman -S package. Always upgrade before installing a package -- particularly if pacman has refreshed the sync repositories. Be very careful when using IgnorePkg and IgnoreGroup for the same reason.

If a partial upgrade scenario has been created, and binaries are broken because they cannot find the libraries they are linked against, do not "fix" the problem simply by symlinking. Libraries receive soname bumps when they are not backwards compatible. A simple pacman -Syu to a properly synced mirror will fix the issue as long as pacman is not broken.